Since any interaction between immiscible fluids depends upon the extent of their physical contact with one another, the rate of such interaction will become a direct function of both the area of interphase surface exposed to one another and the duration of such exposure. Consequently, apparatus requiring such interaction is usually designed to augment the area of interphase contact by dispersing finely divided particles or globules of one phase into a generally continuous stream of another phase. However, the more finely divided the dispersed phase becomes, the more susceptible does it become to entrainment by the continuous phase. Even where two immiscible fluids are merely made to flow through or past one another, the faster their flow relative to one another, the greater will be the frictional drag which will tend to entrain part of each fluid in the other. For this reason, the effective capacity of such apparatus will ultimately be limited by its ability to separate the respective fluids from one another after contact.